Thermal management system and method for electronic assemblies

ABSTRACT

According to an embodiment of the present invention, a thermal management system for an electronic assembly includes an electronic component coupled to a substrate, the substrate coupled to a coldplate, a spring member disposed between and engaging both the electronic component and the coldplate, and a heat transfer element disposed within a chamber formed by the spring member.

TECHNICAL FIELD OF THE INVENTION

This invention relates in general to thermal management of electronicassemblies and, more particularly, to a thermal management system andmethod for integrated circuit packages coupled to circuit boards.

BACKGROUND OF THE INVENTION

Attachment of integrated circuit packages, such as ball grid arrays(“BGAs”), to circuit boards may require careful thermal considerations.For example, attachment of a tile-based transmit/receive (“TR”) modulefor a phased array radar to a circuit board with a BGA approach requiresthat the thermal interface not interfere with the ball attachment. Thethermal interface should be of sufficient flexibility so that it doesnot cause a separation between the TR module and the circuit board byplacing sufficient stress on the solder balls.

Merely having an air interface is not sufficient because the low thermalconductivity of air is not sufficient for heat transfer. Placing solidmaterials between the integrated circuit packages and circuit boardscould meet thermal conductivity requirements, but it would beimpractical because of the tolerances involved. Compliant materialsplaced in the gap would possible mitigate thermal stress concerns on thesolder balls, but compliant materials with high thermal conductivity arenot available.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, a thermalmanagement system for an electronic assembly includes an electroniccomponent coupled to a substrate, the substrate coupled to a coldplate,a spring member disposed between and engaging both the electroniccomponent and the coldplate, and a heat transfer element disposed withina chamber formed by the spring member.

Embodiments of the invention provide a number of technical advantages.Embodiments of the invention may include all, some, or none of theseadvantages. For example, in one embodiment, the use of a spring-likeassembly to keep the top and bottom surfaces in contact with anintegrated circuit package base and coldplate, respectively, allowsadequate thermal coupling and structural integrity. Such assembly causesgood thermal contact to remain in spite of dimension changes that occuras a result of operation over temperature extremes. This assembly may becombined with a concept similar to that of heat pipes to facilitatetwo-phase heat transfer.

Other technical advantages are readily apparent to one skilled in theart from the following figures, descriptions, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional elevation view illustrating a thermalmanagement system for an integrated circuit package coupled to a circuitboard in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention and some of their advantages arebest understood by referring to FIG. 1, like numerals being used forlike and corresponding parts of the various drawings.

FIG. 1 is a cross-sectional elevation view illustrating a thermalmanagement system 100 for an integrated circuit package 102 coupled to acircuit board 104 in accordance with an embodiment of the invention. Inthe illustrated embodiment, integrated circuit package 102 isrepresented as a ball grid array (“BGA”) that is coupled to circuitboard 104 by a plurality of solder balls 106 coupled to respectivecontact pads 107 formed in circuit board 104. However, the presentinvention contemplates other suitable integrated circuit packages orelectronic components coupled to any suitable substrate in any suitablemanner. For example, integrated circuit package 102 may have anysuitable number and type of heat-generating components, such asintegrated circuits 103, coupled to a surface thereof.

Depending on the application for system 100, effective heat dissipationfrom integrated circuit package 102 may be important. Therefore,according to the teachings of one embodiment of the invention, system100 includes a heat transfer assembly 112 disposed between and engagingboth integrated circuit package 102 and a coldplate 110. Coldplate 110may also be coupled to circuit board 104 and may have any suitable sizeand shape and may be formed for any suitable material, such as asuitable metal. In addition, coldplate 110 may be formed from one ormore layers.

Heat transfer assembly 112 transfers heat generated by integratedcircuit package 102 to coldplate 110. In the illustrated embodiment,heat transfer assembly 112 includes a spring member 114 and a heattransfer element 116 disposed within a chamber 115 defined by springmember 114. Heat transfer assembly 112 may also include a fill port 118.In order to obtain effective heat transfer from integrated circuitpackage 102 to coldplate 110, a top portion 121 of spring member 114remains engaged with integrated circuit package 102 and a bottom portion123 of spring member 114 remains engaged with coldplate 110 duringoperation of system 100. Thus, spring member 114 is configured to allowtop portion 121 to exert a force against integrated circuit package 102and bottom portion 123 to exert a force against coldplate 110 duringoperation of system 100. In one embodiment, a distance 125 betweenintegrated circuit package 102 and coldplate 110 is no more thanapproximately 0.25 inch.

In the illustrated embodiment, spring member 114 is formed from twoseparate sheets of material that are coupled at their respective ends inany suitable manner, such as mechanical bonding. Spring member 114 maybe formed from any suitable material, such as a suitable metal and mayhave any suitable size and shape to facilitate the continuous engagementof top portion 121 with integrated circuit package 102 and bottomportion 123 with coldplate 110. Thus, one advantage of the compliantnature of spring member 114 is that it allows heat transfer assembly 112to operate over temperature extremes and to tolerate manufacturingtolerances.

Heat transfer element 116 may include any suitable element thatfunctions to transfer heat from top portion 121 to bottom portion 123 ofspring member 114. Heat transfer element 116 may couple to and/or engageboth top portion 121 and bottom portion 123 in any suitable manner. Itis preferable that heat transfer element 116 stay in contact with bothtop portion 121 and bottom portion 123. Thus, in one embodiment, heattransfer element 116 may be placed in compression during insertion intochamber 115 of spring member 114 so that the top and bottom surfaces ofheat transfer element 116 stay in contact therewith.

In the illustrated embodiment, heat transfer element 116 includes asuitable wicking material, such as a wire mesh formed from any suitablematerial that functions similar to a heat pipe. As such, in oneembodiment, a fluid is disposed in chamber 115 at any suitable pressureso that evaporation of the fluid (i.e. heat removal) occurs at theinterface of top portion 121 and heat transfer element 116 andcondensation of fluid appears at the interface of bottom portion 123 andcoldplate 110. This evaporation and condensation of fluid at therespective locations is continuous throughout operation of system 100 inorder to effectively remove heat from integrated circuit package 102 anddeliver it to coldplate 110. Any suitable fluid is contemplated by thepresent invention, such as water, acetone, methanol, or other suitablefluid.

Thus, during operation of one embodiment of the invention, heat transferassembly 112 facilitates effective heat transfer from integrated circuitpackage 102 to coldplate 110 by keeping top portion 121 in contact withintegrated circuit package 102 and bottom portion 123 in contact withcoldplate 110 while preventing excessive stress from occurring at thesolder balls 106/contact pads 107 interface by relieving those contactareas of having to perform a majority of the heat transfer fromintegrated circuit package 102 to coldplate 110.

Although embodiments of the invention and some of their advantages aredescribed in detail, a person skilled in the art could make variousalterations, additions, and omissions without departing from the spiritand scope of the present invention as defined by the appended claims.

1. A thermal management system for an electronic assembly, comprising:an electronic component coupled to a substrate; the substrate coupled toa coldplate; a spring member disposed between and engaging both theelectronic component and the coldplate; and a heat transfer elementdisposed within a chamber formed by the spring member.
 2. The system ofclaim 1, wherein the electronic component comprises a ball grid array.3. The system of claim 1, wherein the electronic assembly comprises aspace-based antenna.
 4. The system of claim 1, wherein the substratecomprises a circuit board.
 5. The system of claim 1, wherein the springmember comprises a pair of thin metal sheets coupled at their respectiveends.
 6. The system of claim 1, wherein the heat transfer elementcomprises a wicking material.
 7. The system of claim 1, furthercomprising a fill port coupled to the chamber for delivering a fluidinto the chamber.
 8. The system of claim 1, wherein a distance betweenthe electronic component and the coldplate is no more than approximately0.25 inch.
 9. A thermal management method for an electronic assembly,comprising: coupling an electronic component to a substrate; couplingthe substrate to a coldplate; disposing a spring member between theelectronic component and the coldplate such that the spring memberengages both the electronic component and the coldplate; and disposing aheat transfer element within a chamber formed by the spring member. 10.The method of claim 9, wherein the electronic component comprises a ballgrid array.
 11. The method of claim 9, wherein the electronic assemblycomprises a space-based antenna.
 12. The method of claim 9, whereincoupling the electronic component to the substrate comprises couplingthe electronic component to a circuit board.
 13. The method of claim 9,wherein the spring member comprises a pair of thin metal sheets coupledat their respective ends.
 14. The method of claim 9, wherein the heattransfer element comprises a wicking material.
 15. The method of claim9, further comprising coupling a fill port to the chamber and deliveringa fluid into the chamber.
 16. The method of claim 9, wherein a distancebetween the electronic component and the coldplate is no more thanapproximately 0.25 inch.
 17. A thermal management system for anelectronic assembly, comprising: an integrated circuit coupled to acircuit board; the circuit board coupled to a coldplate; a spring memberdisposed between and engaging both the electronic component and thecoldplate; a wicking material disposed within a chamber formed by thespring member; a fluid disposed within the chamber; and wherein a firstsurface of the spring member applies a first force to the integratedcircuit and a second surface of the spring member applies a second forceto the coldplate such that the first member remains engaged with theintegrated circuit and the second member remains engaged with thecoldplate during operation of the electronic assembly.
 18. The system ofclaim 17, wherein the spring member comprises a pair of thin metalsheets coupled at their respective ends.
 19. The system of claim 17,wherein the wicking material comprises a wire mesh.
 20. The system ofclaim 17, further comprising a fill port coupled to the chamber fordelivering the fluid into the chamber.